Case
Kids are making fun of my ELL student

I have one ELL student in my class, and they are beginning to experience teasing because of their accent. They will sometimes stumble over words or mispronounce them, and while I choose to just ignore the mishaps, some of their classmates with laugh or mock the way they spoke. The ELL student doesn't seem to mind, so I don't want to blow it out of proportion and cause an issue if there really isn't one. How do I address this with my class and my ELL student?

Solution #1
Just because the student doesn't show emotion doesn't mean it doesn't bother them. Instead of addressing the whole class you should start with the individual students. I would start with the student who seems to be the "ring leader" if there is one. Starting with them will hopefully make their behavior changes and others will see and follow.